3(x+1)(y+1)-1
elem neutru
3(x+1) (e+1)-1=x
3(x+1) (e+1) =(x+1)
3(x+1) (e+1) -(x+1)=0
(x+1)(3e+3-1)=0,∀x∈D
3e+2=0
e=-2/3
x°x'=-2/3
3(x+1)(x'+1)-1=-2/3
3(x+1)* (x'+1)=1/3
(x+1) (x'+1)=1/9
x'(x+1)+x+1=1/9
x'(x+1)=-x-8/9
x'=- (x+8/9)/(x+1)= -(9x+8)/(9x+9)
admit elemente simetrice toate elementele ∈D\{-1}
